I remember having to stretch my unit as well to get my last ring on and off, perhaps it was too small for me as well. Just out of curiosity last night I put on a ring I had laying around that I had always felt was not quite snug enough. After beginning an edging session I noticed that the veins where much more prominent than usual, and after I few more minutes I took a quick girth measurement and to my surprise the measurement around 1/16 inch less than my measurements during most clamping sessions.
I guess I had always felt this ring was not doing anything because I had no real sensation of pressure while wearing it, yet it seems to be working exactly as advertised. I will give it a few more tries and see how it does, maybe it is a keeper after all.